Annular filter elements are mounted in filter housings to form replaceable filter cartridges which are threadably mounted on internal combustion engines. The cartridges are generally known as "spin-on filters" because they are threadably mountable and removable. If a customer follows the recommended procedures for changing the filter cartridge when lubricating oil is changed, then it is unusual for the filter to clog; however, if the customer fails to change the filter cartridge, or if the lubricating oil becomes contaminated for some other reason, the filter can become clogged and either block or minimize flow of lubricating oil to the engine. If this happens, an engine can be destroyed or seriously damaged.
In order to avoid or at least minimize damage, filter cartridges have been configured to allow oil to bypass filter elements in the cartridges if the filter elements become clogged. The engine is, therefore, supplied with at least unfiltered lubricant rather than either no lubricant at all or insufficient lubricant.
Millions of these filter cartridges are manufactured every year, and millions are disposed of. Since these filter cartridges are disposable, reduction in their cost is highly desirable. One cost reduction approach is to reduce the number of metal parts and the crimping, welding and fastening procedures associated therewith by replacing metal components with the molded plastic components. When this is done, molded plastic components must be configured and arranged so as not to compromise the effective operation of the filter cartridges.